Letter clusters: every letter moves -6

The same question, asked 2 times: 21 Jul 2023 S3*, 26 Jul 2023 S1. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
21 Jul 2023 S3
10 $Which of the following letter-clusters will replace the question mark (?) in the given series to make it logically complete? WUS, QOM, KIG, ?$
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Question 2
26 Jul 2023 S1
7 $Which of the following letter-clusters will replace the question mark (?) in the given series to make it logically complete? ZXV, TRP, NLJ, HFD, ?$
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